参考于 c++手册

String的查找方法 find

使用：

std::string str ("There are two needles in this haystack with needles.");
std::string str2 ("needle");

// different member versions of find in the same order as above:
std::size_t found = str.find(str2);

返回值：

返回第一个匹配的第一个字符的位置。
如果没有找到匹配项，该函数返回string:npos。

static const size_t npos = -1;

下面的Size_t是一个无符号整型(与成员类型相同)。

// string::find
#include <iostream>       // std::cout
#include <string>         // std::string

int main ()
{
  std::string str ("There are two needles in this haystack with needles.");
  std::string str2 ("needle");

  // different member versions of find in the same order as above:
  std::size_t found = str.find(str2);
  if (found!=std::string::npos)
    std::cout << "first 'needle' found at: " << found << '\n';

  found=str.find("needles are small",found+1,6);
  if (found!=-1)
    std::cout << "second 'needle' found at: " << found << '\n';

  found=str.find("haystack");
  if (found!=std::string::npos)
    std::cout << "'haystack' also found at: " << found << '\n';

  found=str.find('.');
  if (found!=std::string::npos)
    std::cout << "Period found at: " << found << '\n';

  // let's replace the first needle:
  str.replace(str.find(str2),str2.length(),"preposition");
  std::cout << str << '\n';
  return 0;
}

输出结果

first’needle’found at: 14
second ‘needle’ found at: 44
‘haystack’ also found at: 30
Period found at: 51
There are two prepositions in this haystack with needles.

上面用了下面的形式

更多string方法

其他方法	作用
string::rfind	Find last occurrence of content in string (public member function)
string::find_last_of	Find character in string from the end (public member function)
string::find_first_of	Find character in string from the end (public member function)
string::find_first_not_of	Find absence of character in string (public member function
string::find_last_not_of	Find non-matching character in string from the end (public member function)
string::replace	Replace portion of string (public member function)
string::substr	Generate substring (public member function)